Minimum Isolation Distances

When you install your well, drainfield, and/or septic tank, you must observe minimum isolation distances as indicated in this table. In some cases, isolation distances must be increased.

Note: If your property is hilly, the well should be located up hill from the drainfield or upstream from your drainfield site.

Minimum Isolation Distances

Item Septic Tank
Drainfield Well**
Property Line
10 feet
10 feet
n/a
Building Foundation (no basement) 5 feet 10 feet 3 feet
Basement Wall 10 feet 15 feet 3 feet
Water Supply Well* (25 feet deep or more) 50 feet 100 feet n/a
Lake or Stream 25 feet 50 feet **

* Isolation distances will be increased for wells serving other than individual dwellings, and may be increased if wells are drawing water from an unprotected aquifer.

** A well cannot be located in an area subject to flooding.

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